Several agencies have begun training recreational divers with oxygen enriched compressed air (EAN). Recreational nitrox diving has in common with traditional compressed air diving the use of nearly all the same equipment and the use of only one gas mix per tank per dive.
Advantages accrue for the user of nitrox in that he/she enjoys a prolonged no-stop time on the basis of “equivalent air depth”, or a safer decompression if one sticks to the air tables-but not both. The advantages are of a prolonged no-stop time are also decreased because at depths shallower than 75 feet the dive is shortened by the limited capacity of the tank and oxygen toxicity safety limits maximum depths to around 120 feet.
Disadvantages of using nitrox include explosive risks and the need to have dedicated equipment that is grease free. Because mistakes can be made in mixing the O2 and air to get the appropriate mixture, each tank needs to be analyzed for O2 content in the presence of the proposed user. Another mistake can be in selection of an inappropriate mixture for the depth of the particular dive. The greatest disadvantage is the risk of drowning from O2 neurotoxicity-the regulator and mouthpiece used by sports divers falling out during a convulsion.
Commercial divers regularly use nitrox but are much safer due to the better control exerted from the surface with the mixture being delivered via a hose and the diver wearing an oro-nasal mask with a helmet or a band-mask and an open-circuit demand regulator, none of which is likely to be lost during a convulsion caused by oxygen neurotoxicity.
Nitrox will be used by the recreational training agencies in open circuit breathing apparatus but it can also be used in closed and semi-closed apparatus. These rebreathers are now being introduced to the recreational diving industry and bring with them the hazards of “soda lime cocktail” and dilutional hypoxia which can lead to unconsciousness without warning and death by drowning.